1. Field of the Invention
This invention relates to a master/slave pump assembly for use in precision metering, multiple component pumping systems in which an auxiliary or slave pump operates in unison with a main or master pump. This invention is also related to dual diaphragm pumps in which a flexible diaphragms pump fluid through a pumping chamber as the diaphragms and a shaft or rod on which they mounted are reciprocated in response to an actuating force, such as a pneumatic force.
2. Description of the Prior Art
U.S. Pat. No. 4,830,586 discloses a double acting diaphragm or dual diaphragm pump that includes two flexible pumping diaphragms connected by a shaft. The diaphragms and the shaft reciprocate in response to alternative pressurization of chambers between the two pumping diaphragms Supplemental pressure chambers in combination with an additional supplemental diaphragm act with the primary pressure chambers and the pumping diaphragms to effectively increase the pressure acting on the fluid within the pumping chambers. This pump also includes an inlet manifold and an outlet manifold communicating with pumping chambers on the outer side of each diaphragm. Ball check valves are provided at the entrance and exit of each pumping chamber.
The ARO 1xe2x80x3 High Pressure 3:1 Ratio (Metallic) Diaphragm Pump is one version of a dual diaphragm pump commercially available from Ingersoll-Rand Company This commercial dual diaphragm pump possesses some of the characteristics of the dual diaphragm pump disclosed in U.S. Pat. No. 4,830,586. This commercially available pump does not appear to include the supplemental diaphragm, but it does include pistons connected to the two pumping diaphragms.
U.S. Pat. No. 6,280,149 discloses an air drive dual diaphragm pump including a linear displacement sensor generating an output voltage proportional to the relative position of a shaft or connecting rod extending between the two diaphragms. Various factors, including the dynamics of the fluid being pumped affect the rate of reciprocation of the diaphragms and the shaft connecting them. For more viscous fluids, the reciprocating rod and diaphragm will reciprocate more slowly for a given air pressure, and the output mass flow rate of viscous fluid will be reduced. One embodiment of an active feedback apparatus includes an inductance coil surrounding ferromagnetic material in the rod. The position of the rod is then dependent upon the inductance of the coil In another embodiment, a linear displacement sensor is disposed next to a diametrically tapered portion and the output voltage potential depends upon the relative position between the linear displacement sensor and the tapered portion. The instantaneous position, velocity and acceleration of the connecting rod can thus be determined. Volumetric displacement of the diaphragm pump and thus be monitored and actual dispensing/metering control, stall prevention, noise control and over travel control are intended benefits of the active feedback An electronic feedback system of this type does not appear to have been previously employed as part of a master/slave pump assembly.
It does not appear that dual diaphragm pumps have been previously employed in a precision metering, multiple component pumping systems in which an auxiliary or slave pump operates in unison with a main or master pump. Such pumps are used to deliver multiple fluids in a metered amount for precise mixing One use of such master/slave pump assemblies is to deliver a resin and a metered amount of catalyst to a mixing zone or mixing element. A precise ratio between the mass flow rate of resin and of catalyst is required for proper operation of such systems. In the fiberglass reinforced product industry, it is essential that the proper ration of catalyst to resin be maintained for proper curing of the finished product. This ratio is not fixed for all applications. Temperature, humidity and product variations can require a different ratio of catalyst to resin. Thus some adjustment of the relative mass flow rates is necessary for any practical assembly. One prior approach that is discussed in U.S. Pat. No. 6,015,268 employs an adjustable linkage between master pump and the smaller volume slave pump. Adjustments can be made by changing the connection between a linking arm and a slave pump drive arm to shorten or lengthen the pumping link arm. U.S. Pat. No. 6,015,268 discloses an adjustable assembly in which an auxiliary or slave pump is coupled to the drive shaft of a master pump by an adjustable rack and pinion gear system. The slave pump is linked to the master pump by a ball joint attached to a yoke of an oscillating quadrant arm coupled to the pinion gear shaft. The amount of secondary or auxiliary fluid, such as a catalyst, is adjusted by adjusting the working length of the oscillating arm. In that patent, an air driven actuator or motor drives coaxial pistons in opposed displacement pumps. It is necessary to seal the pistons relative to their respective cylinders. When the primary fluid, such as a resin used in a fiberglass reinforced product, includes a significant number of abrasive particles or fillers, the life of these seals can be relatively short. The trend is to include more and more additives in resins for a number of reasons, including flammability and other safety related requirements. Therefore, it becomes more and more difficult to operate those pumps for an extended period without replacing damaged seals.
Other prior art master/slave pump assemblies have exposed and separate air motors and fluid or pumping sections that are connected by tie rods at a junction point between the two components. These other prior art assemblies are similar to that shown in U.S. Pat. No. 6,280,149 in that the air motor and the fluid section have an exposed junction point between them where a linkage to a slave pump can be attached. Diaphragm pumps do not have a similar exposed and available attachment point for connecting a linkage between the diaphragm master pump and a slave pump. Attempts have been made to extend the connecting shaft or rod in a diaphragm pump through the fluid pumping section and through the end caps on the diaphragm pump forming one side of the pumping chambers to the exterior of the pump, where a connection can be made to a slave pump However, this approach requires introduction of seals where the extended shaft or rod enters and exits the fluid pumping chamber. These seals, which would normally comprise O-rings would be exposed to the pumped fluid. When an abrasive fluid or a fluid including abrasive particles, fillers or fibers is pumped, such seals are damaged or will rapidly deteriorate resulting in excessive maintenance and down time for such pumps. With the invention described herein no additional seals will be exposed to an abrasive fluid.
This invention comprises an apparatus for pumping plural component fluids at proportional mass flow rates. The apparatus or assembly includes a master pump including a diaphragm for pumping a primary fluid, such as a resin, at a first mass flow rate dependent upon reciprocation of the diaphragm. An intermediate actuator, responsive to movement of the diaphragm, generates an output force dependent upon movement of the diaphragm. This intermediate actuator can be hydraulically or electrically connected, directly or indirectly connected to the diaphragm, or the response can be generated in other ways. The output force from the intermediate actuator drives a slave pump. The slave pump pumps a secondary fluid, such as a catalyst, at a mass flow rate dependent upon reciprocation of the diaphragm. In this manner the primary and secondary fluids can be pumped separately at proportional mass flow rates dependent upon reciprocation of the diaphragm in the master pump. This invention is especially suited for pumping a primary fluid containing abrasive particles, because unlike conventional pumps with elastomeric seals in the flow path of the primary fluid, the diaphragms would not be subject to significant damage or deterioration as a result of exposure to the abrasive particles. The ratio of the primary fluid mass flow rate to the secondary fluid mass flow rate can be altered by an adjustable linkage connecting the intermediate actuator to the slave pump.
This invention also comprises a metering pump assembly for pumping two fluids at flow rates in a ratio independent of the viscosity of the two fluids. This metering pump assembly includes a diaphragm master pump for pumping a first fluid and a slave pump for pumping the second fluid The diaphragm pump includes pump actuation means, such as a pneumatic actuator, and a pumping chamber on at least one side of a diaphragm. A fluid tight chamber is located between the diaphragm and the pump actuation means. In the preferred embodiment, a dual diaphragm pump is employed A hydraulic fluid is disposed in the fluid tight chamber. A hydraulic line communicating between the fluid tight chamber and one side of a slave pump actuating piston so that movement of the diaphragm is communicated to the slave pump actuating piston by the hydraulic fluid. The second pump is driven by movement of the actuating piston. The flow rate of second fluid is therefore dependent upon movement of the diaphragm, which pumps the first fluid, and is independent of the viscosity of the first fluid.